Apparatus for measuring temperatures of iron and steel melts



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APPARATUS FOR MEASURING TEMPERATUHES OF IRON AND STEEL MELTS Filed May 8, 1963 Jn www fw:

nited States 3,264,874 APPARATUS FR MEASURING TEMPERATURES F IRN AND STEEL MELTS Wilhelm Anton Fischer, Ratingen, Germany, assignor to Max-Planck-Institut fr Eisenforschung and Phoenix- Rheinrohr Aktiengesellschaft Vereinigte Httenund Rhrenwerke, both of Dusseldorf, Germany Filed May 8, 1963, Ser. No. 278,829 Claims priority, application Germany, May 30, 1962, M 53,045 1 Claim. (Cl. 7.3-343) In the prior Patent No. 3,091,119, apparatus for continuously measuring the temperature of iron and steel melts is described and claimed. This apparatus comprises a detector head which is held in a tubular passage in the masonry of a melt vessel and includes, at its front end, for dipping into the melt, a refractory ceramic protective tube which jackets a temperature measuring element. The apparatus also comprises a plug of refractory material between the protective tube and the masonry to prevent escape of the melt into the passage. The tubular passage which is formed in the melt vessel masonry, and which may be formed by a number of perforated bricks in a line, or by a tube of highly burned magnesite has a much greater diameter than the protective tube. Consequently, before the detector head is introduced into the tubular passage, the highly refractory ceramic sealing plug is tamped onto the protective tube to ll up the annular gap between the protective tub'e and the wall of the tubular passage. The plug contains, in addition to highly refractory ceramics, a cementing and binding a-gent which melts at the temperature of the masonry, and a substance which evolves gas or vapour at such temperature. Very advantageously, the composition used for the plug is a mixture of substantially equal proportions of a grain size of 0.06 mm. and of a grain size of from 0.12 to 0.25 mm. of the highly refractory substance to which from 1/6 to 1/2 preferably from 1A: to 1/3, of its volume of a from 50% to 70% aqueous solution of waterglass, phosphoric acid or boric acid has been added. After the detector head has been introduced into the tubular passage in the masonry, the ceramic plug which engages around the protective tube is potted by means of an appropriately refractory ceramic potting composition.

Extensive experiments have shown that the porous plug just described is strong enough in bottom-blowing converters to withstand the pressure of the iron melt and chemical attack thereby. The plug can be removed readily from the passage without damaging the passage. However, this plug is not fully satisfactory when the detector head is used to measure the temperature of melts in converters operated solely with oxygen. The reason for this is that, a few minutes after converters of this kind have started blowing, the melt becomes very hot and, because of its high temperature and because of its composition, is very thinly liquid and chemically very active. Also, there is often an interim removal of slag in this process and during the interim removal, the temperature measuring device remains in the hot melt. It has been found in all these cases that iron enters the porous closure plug and makes it so diflicult to 4remove the detector head that continuous temperature measurement during operation becomes almost impossible.

It has been found that these diftiiculties, which arise when the apparatus described in the Patent No. 3,091,119 is operated solely with oxygen, can be obviated if, in accordance with the present invention the diameter of the tubular passage is only slightly greater than the external diameter of the protective tube and the plug of refractory material is initially of a pasty consistency.

ICC

To produce the pasty consistency, less waterglass `is added to the plug than in my prior aforementioned patent. Advantageously, this paste or pulp is first applied to an absorbent backing, such as a strip of bandage mull, which is then Wrapped in a thin layer around the protective tube for the measuring head. Once the protective tube has been introduced into the hot converter, evaporation of the water leads very rapidly to the plug expanding and sintering, so that a durable cl-osure for the detector h'ead is produced.

Additions of graphite, or of electrode carbon in proportions of up to 5%, or of some other carbon-containing substance, such as hard ta-r or hard asphalt, in proportions of up to 15%, to the refractory material further facilitate removal of the detect-or head. Additions of appropriate synthetic `resins can be used instead, if desired. Extended experiments in an LDAC converter have shown that the arrangement hereinbefore described provides satisfactory continuous temperature measurement in the operation of pure oxygen converters.

Advantageously, -the rear end of the protective tube fits in the widened end of an iron tube which engages around the thermocouple lead-in wiring and this tube forms the measuring lance. The widened end lits the tubular passage and forms a backing for the plug.

The tubular passage in the melt vessel masonry may take th'e form of a highly burned perforated brick made of some appropriate basic substance, such as magnesite or dolomite. The bricks external dimensions are the same as the external dimensions of the bricks used for the vessel lining. If the melt vessel masonry is of considerable Wall thickness, the passage can comprise a number of such perforated bricks which may be connected by some sort of tongue and groove arrangement. When the passage is a tube it may be surrounded by an iron tube secured externally to the vessel casing by flanges.

An example of an apparatus in accordance with the invention is illustrated in the accompanying drawings, in which:

FIGURE 1 is a View of the detector head in axial section; and

FIGURE 2 is a sectional view showing how the detector head ts into the wall of the melt vessel.

The head illustrated in FIGURE 1 comprises a ceramic protective tube 1 whose bore 2 receives a thermocouple (not shown) and associated lead-in wires. A plug in the form of a thin layer of a highly refractory ceramic sealant 3 is applied to the forward part of the tube 1 which is about 12 cm. long. The sealant is spread on a strip of bandage mull 3 which, after being coated therewith, is wound around the tube 1. The rear end 1 of the tube 1 lits in a widened end 4 of an iron tube 4 which surrounds the lead-in wires. By means of the tube 4, which serves as a measuring lance, the detector head can be introduced so far into a relatively narrow passage 5 formed by a ceramic guide tube 7 built into a converter lining 6 that the forward end 1 of the tube 1 extends into the converter interior-ie., into the iron melt in the converter. The widened end 4 of the iron tube 4 lits the guide tube 7; a-lso when the detector head is introduced into the passage 5, the end 4 provides a support for the back of the plug 3 which has been applied to the forward part of the tube 1.

Engaging around the guide tube 7, which is made of highly burned magnesite, is a steel tube 8 which extends to the outside of the converter through a passage 9 in the converter casing 10 and through a reinforcing plate 11 welded to the casing. The tube 7 has a flange 12 xed by bolts 13 to the plate 11.

The plug 3 is made of highly refractory ceramic substances or mixture of Substances to which, as well as water glass, carbon-containing substances, such as graphite, ground hard tar or hard asphalt have been added. The sealant expands rapidly inthe heat of the converter to provide a satisfactorily tight and strong connection between the tube 1 and the tube 7 in the converter masonry. When the -tube 1 is worn, however, it can readily be pushed out through th'e tube 4 (after the thermocouple and its wiring have been removed from the detector head). Consequently, the temperature even of iron melts which are very hot and chemically aggressive, as in oxygen blown converters, can be measured satisfactorily during operation.

I claim:

Apparatus for continuously measuring the temperature of iron and steel melts contained in a melt vessel having a masonry wall, comprising a detector head held in a tubular passage in the masonry wall of the melt vessel so that a portion of the front inner end thereof extends into 20 the melt and having at the front inner end thereof a `refractory ceramic protective tube, a temperature measuring elem'ent housed within said tube and a plug of re References Cited by the Examiner UNITED STATES PATENTS 816,428 3/1906 Buck 161-403 X 2,631,179 3/1953 Bell 136-4.77 2,650,206 8/1953 Stock et al 161-433 X 3,038,951 6/1962 Mead 136-4.7 3,091,119 5/1963 Fisher et al 73-343 3,131,115 4/1964 Robitschek 161--191 LOUIS R. PRINCE, Primary Examiner.

D. M. YASICH, Assistant Examiner. 

